1. Field of the Invention
The present invention relates to a voice detection device.
2. Related Background Art
In a voice detection device, there has hitherto been adopted a voice recognition technique in which a speech's voices are handled as acoustic signals and, by carrying out frequency analysis of the acoustic signals, voice information is recognized and processed. As an example of this voice recognition technique, a spectrum envelope or the like is employed. However, in order to yield a good voice detection result by the use of this voice recognition technique, a certain degree of sound volume was necessary at the time of speaking, and detection of the voice information was not possible unless acoustic signals from the speech were input. This, however, disturbs those around the speaker at the time of voice inputting, and hence it is substantially difficult to use such a voice detection device within offices or libraries, or various kinds of public institutions. Besides, there is a problem that in a circumstance where ambient noise is high, a problem of cross talks occurs and hence its voice detection function deteriorates.
Further, in mobile phones having been popularized rapidly in recent years, their users are now required to refrain from using them in trains. This is not only because of electromagnetic influences on electronic medical instruments such as a pace maker or the like at the time of using a mobile phone: A problem with bad behaviors is also pointed out in that one's speaking would turn into a noise disturbing those around him. As regards these problems associated with the acoustic signals, a study has heretofore been made to acquire speech information from something other than acoustic signals. This is because if one could acquire voice information from something other than acoustic information, it would become possible to speak without producing a voice sound.
As an example of this study, there is proposed a voice recognition procedure on the basis of visual information relating to lips (refer to the below-mentioned patent documents 1 and 2). The voice recognition procedures disclosed in the patent documents 1 and 2 specify lips' activities on the basis of image-processing using images picked up by a video camera or the like.
As another example of this study, there is proposed a voice recognition procedure to process myoelectric signals generated in association with perioral muscles activities so as to recognize a kind of a vowel being produced (refer to the below-mentioned non-patent document 1). The voice recognition procedure disclosed in the non-patent document 1 is to discriminate between five vowels (a, i, u, e, o) by counting the number of times a threshold crossing, after passing myoelectric signals through a bandpass filter.
As another example of this study, there is proposed a voice recognition procedure to process myoelectric signals from the perioral muscles using a neural network and detect not only vowels but also consonants (refer to the below-mentioned patent document 3).
As another example of this study, there is proposed a voice recognition procedure to recognize five vowels (a, i, u, e, o) using a root mean square of myoelectric signals at three locations of one's face (refer to below-mentioned non-patent document 2). For this recognition a neural network is used, and hence it is indicated that the recognition can be conducted with a high accuracy.
[Patent Document 1] Japanese Patent Application Provisional Publication No. 52-112205
[Patent Document 2] Japanese Patent Application Provisional Publication No. 6-43897
[Patent Document 3] Japanese Patent Application Provisional Publication No. 7-181888
[Non-Patent Document 1] Noboru Sugie et al., “A speech Employing a Speech Synthesizer Vowel Discrimination from Perioral Muscles Activities and Vowel Production, ” IEE transactions on Biomedical Engineering, Vo. 32, No. 7
[Non-Patent Document 2] Manabe, Hiraiwa and Sugimura, “non-phonation voice recognition using myoelectric signals,” Interaction 2002 Collected Papers, 2002, p. 181-182.